Abstract: Apparatus for determining the bearing of a remotely located source of an inging acoustic signal including a sonobuoy having a submerged package including a hydrophone array for producing omnidirectional and orthogonal directional signals, a combiner for combining the directional signals, and a single channel multiplexer including modulators and a compass driven resolver for providing a single channel multiplexer output signal carrying bearing information in a single frequency channel via a cable to a transmitter unit carried by a surface package of the sonobuoy. The transmitter unit transmits the single channel multiplexed information to a receiver whose output signal is applied to a demultiplexer for deriving a pair of phase shifted signals indicative of the omnidirectional acoustic signal received which pair have a relative phase shift equivalent to the bearing angle referenced to magnetic North.